[Continuing Gamasutra's 2011 roundup is our top 5 PC game selections, including independent games like Binding of Isaac, the official release of Mojang's Minecraft, and CD Projeckt RED's impressive Witcher sequel.]

In 2011, the definition of a "PC game" became increasingly hard to quantify. Indies are flourishing in the space more than ever, and a number of popular PC games are making their way to consoles or even mobile devices. With so many options out there, it became harder to define the quintessential "PC" experience.

While PC gaming, by its loosest definition, includes any game that can be played on a PC, this year Gamasutra chose to only highlight games that are available exclusively on the platform. That means no iOS ports, no console ports, just a single PC release as of 2011.

If there's anything that defines the year's best offerings on PC, it's breadth. All of the titles on our list are worlds apart from each other, ranging from small indie projects to full scale, big budget MMOs. In the end, that variety is part of the beauty of such an open and unrestricted platform.

Absent from this list is Electronic Arts and BioWare's highly-anticipated MMO Star Wars: The Old Republic, which is set to officially debut on December 20th. We don't think its possible to evaluate a large-scale MMO in just a few days, so unfortunately The Old Republic will have to sit this one out.

Here are our picks for the top 5 PC exclusives of 2011:

5. Rift, Trion Worlds

With so many online games adopting the free-to-play model, it's become exceedingly rare to see a traditional, subscription-based MMO. Trion Worlds' Rift, however, is one of those exceptions, and it has managed to find success by sticking to its guns and offering an ambitious, full-scale MMO that justifies its traditional pricing structure.

Outside of its business model, Rift stands out from the MMO crowd with a game world that's constantly changing, allowing the balance of power between monsters and players to shift at many moment. When the game's titular rifts open to introduce an army of monsters into one of the game's zones, players are given the option to team up as a public group to conquer the threat as a team.

This dynamic variation of a traditional MMO framework introduces an exiting layer of unpredictability to the game, and does a great job at encouraging players to play together -- which, after all, is the basic idea behind an MMO.

4. Atom Zombie Smasher, Blendo Games

Blendo Games' Atom Zombie Smasher proves that real-time strategy doesn't need to rely on lighting-fast reflexes or perfect dexterity. Rather, it's a game that encourages thoughtful strategy and impeccable timing to save the population of Neuvos Aires from the out of control zombie outbreak.

In the game, players take a bird's eye view over city districts, and send out helicopters, plant turrets and otherwise take measures to save and protect citizens from the undead horde (represented by abstract, yet still terrifying, purple dots). It's a unique approach to tower defense that constantly has you scrambling to rescue as many people as possible before the city is inevitably overwhelmed.

It's simple, it's abstract, but that's part of its beauty. Atom Zombie Smasher strips away the complex layers of real-time strategy to create a game that really reminds you what makes the genre so great in the first place.

3. The Binding of Isaac, Edmund McMillen and Florian Himsl

Difficulty can be a dangerous element of game design. If your game's too hard, players will get scared away; if it's too easy, it won't hold their attention. The Binding of Isaac, a collaboration between Super Meat Boy's Edmund McMillen and indie dev Florian Himsl, strays on the high end of the difficulty scale, but still finds that perfect balance where you feel compelled to give things another try.

The game follows a traditional roguelike structure, where you fight your way through a labyrinthian series of dungeons, where death is permanent. That's right; die once, and you have to start from the very beginning. With such consequences hanging over your head, each encounter carries much more weight.

Of course, as a roguelike, The Binding of Isaac features randomized maps, which means that even though you might suffer might die over and over, you'll never quite know what to expect on subsequent attempts.

2. Minecraft Version 1.0, Mojang

Sure, Minecraft has been playable for some time now, but in 2011 we saw the game's official debut, and Notch and the team at Mojang have transformed the game considerably over the last year. The game has grown from a construction and survival-based playground into a shockingly deep suite of creative tools featuring new tools, monsters, and even single-player features like quest systems and a definitive end-game.

With all of these new additions, the game has continued to spawn an increasingly impressive array of in-game creations -- players have even found a way to play Minecraft within Minecraft! The game is a real exercise in creative expression, and few other games even come close to the freedom Minecraft allows its players.

With all of the exciting growth the game has seen leading up to its launch, we can't wait to see what happens with Minecraft now that it's seen its official launch.

1. The Witcher 2: Assassins of Kings, CD Projekt RED

There are a number of reasons why The Witcher 2 earned our top spot for 2011. Its well-realized world, ambiguous moral choices, complex combat system, and lengthy campaign are just a few factors that put this ambitious action role-playing game above the competition.

Perhaps the most interesting element of The Witcher 2 is its bold approach to player choice. At key points throughout the game, players are forces to make sweeping decisions that will affect hours and hours of game content, leaving some areas completely unexplored. Considering the amount of work that went into creating the world of the Witcher, it's impressive that CD Projeckt RED had the guts to withhold so much content from players on their first playthroughs.

In another exciting, if risky move, The Witcher 2 puts a lot of trust in the hands of its players, leaving it up to them to explore and master the game's combat and myriad other systems. While it's no doubt challenging at the onset, there's something special in learning to interweave traps, magic, potions, and swordplay to overcome the game's greatest challenges. Of course, since the game's release, CD Prokect RED has added new tutorials and eased the game's steep learning curve, making it even easier to jump into the shoes of Geralt of Rivia.